Table 5: Krause staging system (2000) for inverted papilloma [324].

StageLocation and spreadMalignant changes

T1Tumor totally confined to the nasal cavity, without
extension into the sinuses. (The tumor can be localized
to one wall or region of the nasal cavity or can be bulky
and extensive within the nasal cavity but must not
extend into the sinuses or into extranasal
compartment)
There must be no
concurrent malignancy

T2Tumor involving the ostiomeatal complex, and ethmoid
sinuses, or the medial portion of the maxillary sinus,
with or without involvement of the nasal cavity.
There must be no
concurrent malignancy

T3Tumor involving the lateral, inferior, superior, anterior,
or posterior walls of the maxillary sinus, the sphenoid
sinus, or the frontal sinus with or without involvement
of the medial portion of the maxillary sinus, the ethmoid
sinuses, or the nasal cavity
There must be no
concurrent malignancy

T4All tumors with any extranasal/extrasinus extension to
involve adjacent, contiguous structures such as the
orbit, the intracranial compartment, or the
pterygomaxillary space
All tumors associated
with malignancy